The fluid that is recovered from the formation during the drill stem test of a well accumulates in the pipe string that suspends the test tools. For safety reasons, it is desirable to remove the fluid recovery from the pipe string before withdrawing the tools when the test is completed, or else the fluids may be spilled on the rig floor as pipe joints are disconnected and thereby constitute a considerable fire hazard.
Thus it is common practice to incorporate in a string of drill stem testing tools a component generally known as a reversing valve. A reversing valve is a tool that includes a normally closed valve element which can be opened through suitable mechanical manipulation or pressure changes to provide open communication between the well annulus and the tubing string at a point above the main test valve so that pressure applied to the well annulus can displace the fluid recovery upwardly to the surface where it can be piped to suitable containers or the like.
Most reversing valves are designed such that once they have been opened, they cannot be reclosed. Of course, it will be recognized that with an open communication path between the annulus and the tubing string, it is not generally possible to perform any further testing of the well or any pressure services such as fracturing or acidizing without removing the tools from the well in order to reposition the reversing valve in its normally closed position.
A known reversing valve that can be reclosed without removing it from the well is disclosed in Evans et al., U.S. Pat. No. 4,113,012 issued Sept. 12, 1978. The device disclosed in this patent is annulus pressure responsive, and has a rather complicated system of vertically spaced cam teeth on an index sleeve that coact with lugs on a control mandrel to provide for multiple valve positions and eventual reclosure. However the applicant does not consider an annulus pressure actuated device of the type described to be the better approach for several reasons. For one thing, various other tools in the test string may be annulus pressure operated, so that the Evans et al. valve may be opened at an undesirable time in response to such pressure changes. Moreover, the reference device is structurally quite complicated and accordingly is believed to be rather costly to manufacture and troublesome to maintain.
It is the general object of the present invention to provide a new and improved pressure controlled reversing valve that can be opened and then reclosed while the valve remains in the well.
Another object of the present invention is to provide a new and improved pressure controlled reversing valve that can be opened and then reclosed in response to pressure changes applied to the fluids in the pipe string in which the valve is connected to provide for improved operator control over the sequence of tool component actuation during a well testing operation.
Still another object of the invention is to provide a new and improved pressure controlled reversing valve of the type described that is more economical to manufacture and easier to maintain in operative condition for repeated usage in well testing operations.